tsk - about your bird calls;
First recommendation is to install an app called Samsung DeX - this app will allow you to use a USB cable to your computer and then display the phone screen onto the computer monitor. It also includes a file transfer app for your phone.
Using the "My Files" app, you can locate your old recordings - according to google, your Merlin files are stored in the folder Music/Merlin. The tech may have put them into the folder internal storage/Music/Samsung - drag and drop to the correct folder if that occurred.
The other possibility to check first is permissions under "Settings > apps > Merlin > Permissions and verify that Merlin has permission for Microphone.